3b very loud knock suddenly started - clutch explosion??

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Jun 20, 2007
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Tahsis, BC
Started feeling a slight vibration when changing gears.

After about 10-20 minutes I was driving in 5th and things seemed to go haywire (clutch slip I think?) and an extremely loud knock started causing me to pull over and turn off engine.

Knock is in time with RPMs

Initial look under hood couldn't find source, sounds like it's coming from engine. Can feel it in clutch pedal.


Clutch was known to have oil leaking onto it. My initial assumption and HOPE is that the clutch exploded in some way. However, can still drive and engage/disengage clutch, so that seems unlikely?

Engine recently rebuilt, with a turbo/intercooler. Knock does not seem to be coming from turbo.

Heeelp!!
 
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Not good news best get it back to the engine builder or a mechanic ASAP on a float don't drive as this could destroy engine.
 
Joined
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Well it DOES chatter like crazy.... I'm still optimistic...

Will let you all know what happens when I pull off the bell housing in a few days
 
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Jul 15, 2006
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How did this turn out? Your description sounds like my situation> Had tranny out for rear main seal. A couple days after getting it back together it started knocking. Very noticeable in the clutch pedal when depressed. No clutch chatter. Engine starts right up and runs well.
 

RufusTheDufus

DieselUpdate.com
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I had a somewhat similar experience before my crankshaft snapped.

I think I drove about 2500 miles with a slightly bent crankshaft. (Possibly more, the engine always had a bad vibration but I didn't realize how bad until I swapped in a replacement.) I had feedback in the clutch pedal and some chattering like the pressure plate was wet with oil mist.

In my engine noise wasn't like rod knock or lower end noise. It sounded like a really bad exhaust leak or valve noise and it would get worse when on-boost (10psi) climbing hills or accelerating. I adjusted the valves 3 times in 2500 miles and it never made a difference. Couldn't figure it out. Couldn't find an exhaust leak and continued on my trip.

The crank snapped 5 hours south of Laredo, TX near Saltillo, Mexico.

The noise that sounded like an exhaust leak was the flywheel rubbing on the spacer plate between that goes between the block and the trans. Mine plate is modified, it's from a 70series/aluminum bell housing but I mated the engine to a cast iron H55F bell housing. I had to clearance an area of the plate so the starter would mount properly. The plate wasn't completely flat near the starter area. It seemed when the engine was under load the flywheel would deflect just enough that one of the weights on the back would make just enough contact to sound like valve noise/exhaust leak.
 
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I'm wondering which end to start with? Dropping the oil pan seems like the least invasive but since I just had the trany out and I feel it in the peddle when pushed in is that the place to start? I saw @gerg helping a fellow mudder with a knock that sounded like mine and it was the head gasket. I have a MLS HG in mine. Any input is appreciated.
 

gerg

 
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Jun 13, 2005
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When mine broke my clutch pedal was moving alot. Very weird feeling. Drop the pan and inspect crank closely. My crack was not easy to find. When it broke it was very loud and shook the truck.
 
Last edited:

samwise

 
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May 4, 2008
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Im probably the guy your talking about that @gerg helped, although hes helped lot of us. Last fall mine was making noise, turned out to be the head gasket, sounds like you read my post. I never felt it in my clutch pedal that I recall though.
Ive also had a broken crank, it was just a sudden knocking sound could feel in the whole truck, very obvious something was wrong.

Hopefully not something big, but would suck to pull the trany again.
 
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Thanks guys. I appreciate the input and knowledge put fourth. The inspection will start soon. I'm just about over the disappointment of taking it apart again.
 

gerg

 
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I was so disheartened when mine broke. Don't let it get you down. Pull that crank and get it back on the road for summer! Delaying starting a project always takes more time than the project itself so get into it asap.
 
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